This invention relates generally to electrophotographic copiers, and more particularly to an electrophotographic copier for making multicolor reproductions of a multicolor original document.
In making multicolor reproductions with an electrophotographic copier, typically a light image of a multicolor original document is projected through primary color filters (red, green, and blue) to form color separation images. The color separation images expose a moving electrostatically charged photoconductive member. Exposure may take place sequentially by illuminating the document three times, and projecting the light images respectively through the color filters, or simultaneously by illuminating the document once and dividing the light image into color separation images such as by beam splitters or dichroic mirrors. Exposure forms latent image charge patterns in spaced areas on a photoconductive member corresponding to the color separation images. The latent image charge patterns are respectively developed with complimentary colored toner material (e.g., cyan, magenta, and yellow). The developed images are then transferred to a receiver sheet in registered superimposed relationship to form a multicolor reproduction of the multicolor original.
In an alternative color copier configuration, separation electrostatically charged photoconductive members are exposed by respective color separation images to form the latent image charge patterns. Of course, with plural photoconductive members, there is a duplication of certain of the copier mechanisms (e.g., photoconductive members, chargers, cleaning apparatus). However, steps of the copying process can be carried out in parallel. This results in an equal number of copies being reproduced per unit time (with respect to apparatus having one photoconductive member) at relatively reduced photoconductive member and receiver sheet transport velocities.
Optical mechanisms for exposure of the photoconductive member(s) in prior art color copiers are complex (see, for example, U.S. Pat. No. 3,690,756 issued Sept. 12, 1972 in the name of Smith, and U.S. Pat. No. 3,841,751 issued Oct. 15, 1974 in the name of Draugelis et al). The complexity arises, in part, from the need to space the elements of the optical mechanisms and accurately align the elements in their relative positions to insure projection of the respective light images toward desired spaced locations.